Meson Decay Constants Research Articles

Scale setting and hadronic properties in the light quark sector with ( 2+1 )-flavor Wilson fermions at the physical point

We report scale setting and hadronic properties for our new lattice QCD gauge configuration set (HAL-conf-2023). We employ (2+1)-flavor nonperturbatively improved Wilson fermions with stout smearing and the Iwasaki gauge action on a 964 lattice, and generate configurations of 8000 trajectories at the physical point. We show the basic properties of the configurations such as the plaquette value, topological charge distribution and their autocorrelation times. The scale setting is performed by detailed analyses of the Ω baryon mass. We calculate the physical results of quark masses, decay constants of pseudoscalar mesons and single hadron spectra in light quark sector. The masses of the stable hadrons are found to agree with the experimental values within a subpercent level. Published by the American Physical Society 2024

Charm physics with overlap fermions on 2+1-flavor domain wall fermion configurations* *Supported in part by the National Key Research and Development Program of China (2020YFA0406400, 2023YFA1606002), the National Natural Science Foundation of China (12075253, 11935017, 12192264, 12293060, 12293065, 12293063, 12070131001), CRC 110 by DFG and NNSFC. Keh-Fei Liu is supported by the U.S. DOE Grant (DE-SC0013065) and DOE Grant (DEAC05-06OR23177),

Decay constants of pseudoscalar mesons D, , and vector mesons , , are determined from the lattice QCD at a lattice spacing fm. For vector mesons, the decay constants defined by tensor currents are given in the scheme at GeV. The calculation is performed on domain wall fermion configurations generated by the RBC-UKQCD collaborations and the overlap fermion action is used for the valence quarks. Comparing the current results with our previous results at a coarser lattice spacing fm provides a better understanding of the discretization error. We obtain with a better precision than our previous result. Combining our MeV with the total width of determined in a recent study gives a branching fraction for leptonic decay.

Theoretical overview on heavy flavor physics at LHCb

Precise prediction of the heavy hadrons decay amplitudes is of great importance in the determination of the parameters of KM matrix and searching for new physics signals beyond the standard model. Due to the high accuracy of the B meson decay constants, the structure dependent QED corrections should be taken into account for B→μ+μ− decays due to the power enhancement, but this effect is numerically negligible for B→τ+τ−. The radiative leptonic decays and double radiative decays are the best channels to determine the B meson distribution amplitudes, but one should systematically deal with the power corrections to reduce the uncertainty. The heavy-to-light form factors is one of the most important nonperturbative quantities, and an improved method to improve the theoretical accuracy is to fit the form factors using combined data from Lattice and light-cone sum rules which works well at large recoil region. The power suppressed weak annihilation contribution is phenomenologically important in the nonleptonic decays, and the previously neglected hard-collinear gluon exchange diagrams have the potential to cancel the endpoint singularity arising from the hard gluon exchange. Therefore, more endeavors need to be paid to this topic.

Hadronic physics from a Wilson fermion mixed-action approach: charm quark mass and D(s)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$D_{(s)}$$\\end{document} meson decay constants

We present our first set of results for charm physics, using the mixed-action setup introduced in a companion paper [1]. Maximally twisted Wilson valence fermions are used on a sea of non-perturbatively O(a)-improved Wilson fermions, made up by CLS Nf=2+1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$N_\\mathrm {\\scriptstyle f}=2+1$$\\end{document} ensembles. Our charm-sector observables are free from O(amc)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$O(am_c)$$\\end{document} discretisation effects, without need of tuning any improvement coefficient, and show continuum-limit scaling properties consistent with leading cutoff effects of O(a2)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$O(a^2)$$\\end{document}. We consider a subset of CLS ensembles – including four values of the lattice spacing and pion masses down to 200 MeV – allowing to take the continuum limit and extrapolate to the physical pion mass. A number of techniques are incorporated in the analysis in order to estimate the systematic uncertainties of our results for the charm quark mass and the D(s)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$D_{(s)}$$\\end{document}-meson decay constants. This first study of observables in the charm sector, where the emphasis has been on the control of the methodology, demonstrates the potential of our setup to achieve high-precision results.

Spin averaged mass spectra and decay constants of heavy quarkonia and heavy-light mesons using bi-confluent heun equation

Spin averaged mass spectra and decay constants of heavy quarkonia and heavy-light mesons using bi-confluent heun equation

Phase structure of the on-shell parametrized 2+1 flavor Polyakov quark-meson model

Augmenting the improved chiral effective potential of the on-shell renormalized 2+1 flavor quark-meson (RQM) model with the Polyakov-loop potential that accounts for the deconfinement transition, we get the quantum chromodynamics (QCD)-like framework of the renormalized Polyakov quark-meson (RPQM) model. When the divergent quark one-loop vacuum term is included in the effective potential of the quark-meson (QM) model, its tree-level parameters, or the parameters fixed by the use of meson curvature masses, become inconsistent as the curvature masses involve the self-energy evaluations at zero momentum. Using the modified minimal subtraction method, the consistent chiral effective potential for the RQM model has been calculated after relating the counterterms in the on-shell scheme to those in the MS¯ scheme and finding the relations between the renormalized parameters of both the schemes where the physical (pole) masses of the π, K, η, and η′ pseudoscalar mesons and the scalar σ meson, the pion and kaon decay constants, have been put into the relation of the running couplings and mass parameter. Using the RPQM model and the PQM model with different forms for the Polyakov-loop potentials in the presence or the absence of the quark backreaction, we have computed and compared the effect of the consistent quark one-loop correction and the quark backreaction on the scaled chiral order parameter, the QCD phase diagrams, and the different thermodynamic quantities. The results have been compared with the 2+1 flavor lattice QCD data from the Wuppertal-Budapest Collaboration [ 73, ] and the HotQCD Collaboration []. Published by the American Physical Society 2024

D(s)− mesons semileptonic form factors in four-flavor holographic QCD

We investigate semileptonic form factors of a D(s) meson from a modified soft-wall 4-flavor holographic model. The model successfully reproduces the masses and decay constants of various mesons, including ρ, K*, D*, Ds*, a1, K1, f1, D1, Ds1, π, K, η, D, and Ds. Moreover, we study the semileptonic decay processes D+→(π,K,η)l+νl and Ds+→(K,η)l+νl, associated with the vector meson exchange, as well as D(s)+→Kl+νl, associated with the vector and axial vector meson exchange. The form factors f+(q2) for D→π and D(s)→K decays agree excellently with experimental and lattice data, outperforming other theoretical approaches. The f+(q2) form factor for D+→η is compatible with experimental data, while a slight discrepancy is observed for Ds+→η at large q2. Additionally, we predict the vector form factors V(q2) and A1(q2) for D→K and Ds→K decays, respectively. The results agree well with other approaches and lattice data at maximum recoil (q2=0). Published by the American Physical Society 2024

Heavy–Light meson spectroscopy with strong coupling at N2LO level in V-scheme

The quark–antiquark potential is one of the basic ingredients of QCD-inspired potential models. This work will report the results of the masses and decay constants of heavy-flavor pseudo-scalar mesons within a QCD-based potential model having both inverse distance Coulomb and the linear confinement pieces. To that end, we use the inverse piece incorporating two-loop effects as suggested in V-scheme. Quantum mechanical perturbative methods: Dalgarno’s method of perturbation theory and variationally improved perturbation theory are used for the investigation. We use the Coulombic piece as the parent which is allowed by both Dalgarno’s perturbation theory and variationally improved perturbation theory. The results are compared with the latest updated theoretical predictions and PDG data. The sensitivity of the input parameters of the model has been discussed.

Pseudoscalar meson decay constants and distribution amplitudes up to the twist-4 in the light-front quark model

Pseudoscalar meson decay constants and distribution amplitudes up to the twist-4 in the light-front quark model

Independence of current components, polarization vectors, and reference frames in the light-front quark model analysis of meson decay constants

The issue of resulting in the same physical observables with different current components, in particular from the minus current, has been challenging in the light-front quark model (LFQM) even for the computation of the two-point functions such as meson decay constants. At the level of one-body current matrix element computation, we show the uniqueness of pseudoscalar and vector meson decay constants using all available components including the minus component of the current in the LFQM consistent with the Bakamjian-Thomas construction. Regardless of the current components, the polarization vectors, and the reference frames, the meson decay constants are uniquely determined in the noninteracting constituent quark and antiquark basis while the interactions of the constituents are added to the meson mass operator in the LFQM.

Airy function, mass spectra and decay constants of pseudo-scalar heavy-flavor mesons at N3LO level in a perturbative approach

In this paper, we incorporate three-loop contributions in the strong coupling constant and study their effects in the wave functions, masses and decay constants of heavy–light pseudo-scalar mesons (PSM) [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] in V-scheme. In this work, we use the standard linear plus inverse distance QCD potential in association with Dalgarno’s method of perturbation theory for linear parent option. Detailed comparison is done with the results from Lattice QCD, QCD sum rules, light-front quark model (LFQM), relativistic harmonic confinement model (RHCM) and recent PDG data.

Nonrelativistic quark model for mass spectra and decay constants of heavy-light mesons using conformable fractional derivative and asymptotic iteration method

In this paper, we use the concept of conformable fractional derivative to study the nonrelativistic radial Schrödinger equation. We suggest an extended version of the Cornell potential as the quark–antiquark interaction of light and heavy mesons. We generalize the asymptotic iteration method to the fractional domain. The latter is used to calculate the energy eigenvalues, as well as the effect of the fractional order [Formula: see text] on energy spectra. To test the applicability of our model, we use the obtained results to reproduce the mass spectra of some light and heavy mesons such as [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] quarks. The mass spectra are obtained at different values of the fractional order parameter [Formula: see text] and were compared with experimental results and other relevant theoretical works. Using the wave function, we calculated the decay constants for heavy-light [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] mesons. Our results are found to be in good agreement with the experimental data, and improved in comparison with other theoretical previsions.

Solving hadron structures using the basis light-front quantization approach on quantum computers

Quantum computing has demonstrated the potential to revolutionize our understanding of nuclear, atomic, and molecular structure by obtaining forefront solutions in nonrelativistic quantum many-body theory. In this work, we show that quantum computing can be used to solve for the structure of hadrons, governed by strongly interacting relativistic quantum field theory. Following our previous work on light unflavored mesons as a relativistic bound-state problem within the nonperturbative Hamiltonian formalism, we present the numerical calculations on simulated quantum devices using the basis light-front quantization approach. We implement and compare the variational quantum eigensolver and the subspace-search variational quantum eigensolver to find the low-lying mass spectrum of the light meson system and its corresponding light-front wave functions as quantum states from ideal simulators, noisy simulators, and IBM quantum computers. Based on obtained quantum states, we evaluate the meson decay constants and parton distribution functions directly on the quantum circuits. Our calculations on the quantum computers and simulators are in reasonable agreement with accurate numerical solutions solved on classical computers when noises are moderately small, and our overall results are comparable with the available experimental data.

Center of mass motion in bag model

Despite its success with mass spectra, the reputation of the bag model has been marred by embarrassment of the center of mass motion. It leads to severe theoretical inconsistencies. For instance, the masses and the decay constants would no longer be independent of the momentum. In this work, we provide a systematic approach to resolving this problem. Our framework can consistently compute the meson decay constants and baryon transition form factors. Notably, the form factors in the neutron β decays do not depend on any free parameters and are determined to be and or , which is close to the experimental value of . In addition, we find that , which agrees to the experimental value of .

B → D1(2420) and B → {mathrm{D}}_1^{prime } (2430) form factors from QCD light-cone sum rules

We perform the first calculation of form factors in the semileptonic decays B → D1(2420)ℓνℓ and B → {D}_1^{prime } (2430)ℓνℓ using QCD light-cone sum rules (LCSRs) with B-meson distribution amplitudes. In this calculation the c-quark mass is finite. Analytical expressions for two-particle contributions up to twist four are obtained. To disentangle the D1 and {D}_1^{prime } contributions in the LCSRs, we suggest a novel approach that introduces a combination of two interpolating currents for these charmed mesons. To fix all the parameters in the LCSRs, we use the two-point QCD sum rules for the decay constants of D1 and {D}_1^{prime } mesons augmented by a single experimental input, that is the B → D1(2420)ℓνℓ decay width. We provide numerical results for all B → D1 and B → {D}_1^{prime } form factors. As a byproduct, we also obtain the D1- and {D}_1^{prime } -meson decay constants and predict the lepton-flavour universality ratios R(D1) and R( {D}_1^{prime } ).

Semileptonic D meson decays to the vector, axial vector and scalar mesons in Hard-Wall AdS/QCD correspondence

In this work, a Hard-Wall AdS/QCD model with 4 flavours is utilized to calculate the transition form factors for the semileptonic Drightarrow (V, A, S),ell ,nu _{ell }. These decays occur by c rightarrow d,ell ,nu _{ell } transition at quark level for D^{0} rightarrow rho ^{-}(b_{1}^{-}, a_{1}^{-}, a_{0}^{-}),ell ,nu _{ell }, D_{s}^{+} rightarrow K_{0}(K_{1A}^{0}, K_{1B}^{0}),ell ,nu _{ell } decays while the semileptonic decays D^{0} rightarrow K^{_{*-}}(K_{1A}^{_-}, K_{1B}^{_-}, K_{0}^{_-})ell ,nu _{ell } and D^{+} rightarrow {bar{K}}_{0}({bar{K}}_{1A}^{0}, {bar{K}}_{1B}^{0}),ell ,nu _{ell } proceed by c rightarrow , s, ell ,nu _{ell } transition. The masses and decay constants of scalar mesons as well as the form factors and the branching ratios of aforementioned decays are calculated in our model, and a comparison is also made between our results and predictions of other theoretical methods and the existing experimental values.

Meson masses and decay constants in holographic QCD consistent with ChPT and HQET

We focus on the chiral and heavy quark mass expansion of mesons masses and decay constants. We propose a light-front QCD formalism for the evaluation of these quantities, consistent with chiral perturbation theory and heavy quark effective theory.

Spontaneous chiral symmetry breaking in holographic soft wall models

We investigate nonlinear extensions of the holographic soft wall model proposed by Karch et al. [Phys. Rev. D 74, 015005 (2006)] including nonminimal couplings in the five-dimensional action. The nonminimal couplings bring a new parameter ${a}_{0}$ which controls the transition between spontaneous and explicit symmetry breaking near the limit of massless quarks (the chiral limit). In the physical region (positive quark mass), we show that above a critical value of the parameter ${a}_{0}$ the chiral condensate $⟨\overline{q}q⟩$ is finite in the chiral limit, signifying spontaneous chiral symmetry breaking. This result is supported by the lightest states arising in the spectrum of the pseudoscalar mesons, which become massless in the chiral limit and are therefore intrepreted as Nambu-Goldstone bosons. Moreover, the decay constants of the pseudoscalar mesons also support this conclusion, as well as the Gell-Mann-Oakes-Renner relation satisfied by the lightest states. We also calculate the spectrum of scalar, vector, and axial-vector mesons with their corresponding decay constants. We describe the evolution of masses and decay constants with the increasing of the quark mass, and for the physical mass, we compare our results against available experimental data. Finally, we do not find instabilities in our model for the physical region (positive quark mass).

Chiral dynamics with confinement versus the standard chiral theory

Chiral dynamics is investigated using the chiral confining Lagrangian (CCL), previously derived from QCD with confinement interaction. Based on the calculations of the quark condensate, which is defined entirely by confinement in the zero quark mass limit, one can assert that chiral symmetry breaking is predetermined by confinement. It is shown that CCL retains all basic relations of the standard chiral theory but enables one to include quark degrees of freedom in the CCL. The expansion of the CCL provides the Gell–Mann–Oakes–Renner (GMOR) relations and the masses and decay constants of all chiral mesons, including [Formula: see text]. For the latter, one needs to define a nonchiral component due to confinement, while the orthogonality condition defines the wave functions and the eigenvalues. The resulting masses and decay constants of all chiral mesons are obtained in good agreement with the experimental and lattice data.

The negative-parity spin-1/2 Λ baryon spectrum from lattice QCD and effective theory

The spectrum of the negative-parity spin-1/2 Λ baryons is studied using lattice QCD and hadronic effective theory in a unitarized coupled-channel framework. A direct comparison between the two approaches is possible by considering the hadronic effective theory in a finite volume and with hadron masses and mesonic decay constants that correspond to the situation studied on the lattice. Comparing the energy level spectrum and SU(3) flavor decompositions of the individual states, it is found that the lowest two states extracted from lattice QCD can be associated with one of the two Λ(1405)-poles and the Λ(1670) resonance. The quark mass dependences of these two lattice QCD levels are in good agreement with their effective theory counterparts. However, as current lattice QCD studies still rely on three-quark operators to generate the physical states, clear signals corresponding to the meson-baryon scattering states, that appear in the finite volume effective theory calculation, are not yet seen.